Myrtle Wilson's sister Catherine in The Great Gatsbyis a stereotypical flapper. Nick meets her at the apartment party with Myrtle and Tom in Chapter 2. Fitzgerald's description of Catherine's Bohemian style and her conversation with Nick clearly represent the carefree flapper lifestyle of the 20s.

Catherine, despite her apparent frivolousness and laid-back attitude in Chapter 2, is a very loyal sister. After Gatsby's murder and the ensuing inquest, Catherine--when questioned--never mentions her sister's affair with Tom Buchanan. Of course, she might have also had more selfish motivation for keeping quiet. Instead of simply protecting her late sister's name, perhaps she was paid off by the Buchanans as they retreated into their cocoon of wealth, or perhaps she didn't want to be associated with a compromising affair that might hinder her chances to move upward in society. It is difficult to know what her true motivation is. Nonetheless, Fitzgerald does clearly present her as a traditional flapper at the novel's beginning.

It should also be noted that it is Catherine that is used by the author to let us know more about Tom and Myrtle's relationship. It would have seemed odd coming from Myrtle or Tom directly. She plays a significant role in allowing us to understand Tom's feelings about Myrtle and how he is still trying to maintain a relationship with Daisy.